A steering device transmits a motion of a steering shaft, rotating by the operation of a handle, to a pinion shaft as an input shaft of a steering gear. The direction of a vehicle wheel is changed by the transmitted motion of the steering gear. In general, the rotation axis of the steering shaft and the axis of the pinion shaft are not provided on the same straight line. Therefore, an intermediate shaft is provided between the steering shaft and the steering gear with a universal joint therebetween, and the end of the intermediate shaft is coupled to the steering shaft. Further, the end of the intermediate shaft is coupled to the end of the pinion shaft through the universal joint. Due to the presence of two components, the universal joint and the intermediate shaft, power is transmitted between the steering shaft and the input shaft of the steering gear which are not present on the same straight line.
The intermediate shaft is disposed in a three-dimensional space between the steering shaft and the pinion shaft. In order to rotate the steering shaft and the pinion shaft at the same angular velocity, the intermediate shaft module needs to be disposed so that the angle formed between the rotation axis of the steering shaft and the rotation axis of the intermediate shaft is equal to the angle formed between the axis of the steering gear and the rotation axis of the intermediate shaft. Further, in recent years, the steering device which operates the vehicle wheel of the vehicle is designed by a simulation technique. For example, there are techniques disclosed in Patent Literature 1 to Patent Literature 3.